Reading the Blueprints of Creation

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HOW TO SURVEY THE COSMOS IN FOUR NOT-SO-EASY STEPS THE SLOAN DIGITAL SKY SURVEY, the most advanced of the current generation of astronomical surveys, is compiling an atlas of a quarter of the sky. It will take five years, using a dedicated 2.5-meter telescope atop Apache Point in New Mexico. 1 2 THE TELESCOPE operates in camera mode on clear nights, taking pictures through five color filters at the rate of 20 square degrees an hour—netting millions of celestial bodies per night. GALAXIES and other objects are identified by software and selected for follow-up spectroscopy. The object shown here is the spiral galaxy UGC 03214 in the constellation Orion. 3 1.0 4 0.8 Relative Flux 0.6 0.4 0.2 S D S S C O L L A B O R A T I O N OPTICAL FIBERS are plugged into a metal plate with 640 holes. Each fiber channels light from a celestial body to a spectrograph, which operates when the sky is not so clear. 0 400 600 800 Wavelength (nanometers) THE SPECTRA THAT RESULT provide a precise way to classify objects. From them, astronomers also determine the redshifts, hence distances, of the objects. w w w . s c i a m . c o m S C I E N T I F I C A M E R I C A N 57 COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.
COSMIC MAPS THESE WEDGE-SHAPED FIGURES show the distribution of galaxies (dots) in two volumes of space. The third dimension, which spans an angle of several degrees, has been flattened. The figures reveal two dramatic “Great Walls” containing thousands of galaxies each, as well as filaments and voids at all scales. Millions of Light-Years 600 500 400 300 200 100 MILKY WAY 1,732 Galaxies REDSHIFT SURVEY by the Harvard-Smithsonian Center for Astrophysics (CfA) in the mid-1980s discovered the first Great Wall but was too limited to apprehend its full extent. 9h 16h CFA GREAT WALL 1,200 1,100 1,000 900 800 700 9h Millions of Light-Years 10h 10h SLOAN DIGITAL SKY SURVEY, which is now under way, covers a much larger volume. It found another Great Wall more than one billion light-years long. The region shown above is about 1 percent of the full Sloan volume. The bull’s-eye diagram (right) covers a volume six times as large; the outline indicates the location of the above wedge. The concentric circles indicate distance in millions of light-years. 11h 11h 12h 13h 14h Location in Sky (right ascension, in hours) 12h 12h 10h 14h 15h 8h 16h 11,246 Galaxies 13h 14h SLOAN GREAT WALL 6h 4h 2,000 1,500 2h 1,000 500 0h 22h 20h 18h 52,561 Galaxies B R Y A N C H R I S T I E D E S I G N ; S O U R C E S : J . R I C H A R D G O T T A N D M A R I O J U R I C P r i n c e t o n U n i v e r s i t y ( w e d g e ) ; S D S S C O L L A B O R A T I O N ( b u l l ’ s - e y e ) 58 S C I E N T I F I C A M E R I C A N F E B R U A R Y 2 0 0 4 COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.
Page 1 and 2: SPECIAL REPORT R By EADING THE BLUE
Page 3: determine their redshifts and infer
Page 7 and 8: BUILDING A UNIVERSE TO CONNECT THE

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